A sparse non-orthogonal multiple access manner is a new multiple access manner. In this access manner, multiple users use a same time-frequency resource block. Each resource block includes several resource elements (RE). The resource elements may be subcarrier-symbol units in an orthogonal frequency division multiplexing (OFDM) technology, or may be time-domain or frequency-domain resource elements in another air-interface technology.
A sparse non-orthogonal multiple access system is similar to an OFDM system, and only a modulation encoder and a modulation decoder in the OFDM system are replaced with an encoder and a decoder corresponding to sparse non-orthogonal multiple access. In a Long Term Evolution (LTE) system, if decoding fails at a decode end, decoding error data is sent again by using a hybrid automatic repeat request (HARQ) system. The HARQ system is a system obtained after forward error correction (FEC) is introduced into an automatic repeat request system. FEC may be used for correcting a data error in a transmission process. If the data error is in an error-correction range of FEC, the error is corrected by using FEC, and the decode end feeds back hybrid automatic repeat request acknowledgement (HARQ-ACK, HARQ Acknowledgement) information to a transmit end. If the data error goes beyond an error-correction range of FEC, the decode end feeds back hybrid automatic repeat request negative acknowledgement (HARQ-NACK, HARQ Negative Acknowledgement) information to a transmit end. The HARQ-ACK and the HARQ-NACK are collectively referred to as HARQ information.
In an existing LTE system, on a physical uplink shared channel (PUSCH), user equipment implements multiplexing of HARQ information and uplink transmission data in a frequency band of the user equipment. This HARQ information transmission method is applicable to a system without frequency domain multiplexing. However, for some systems such as a sparse code multiple access (SCMA) system, multiple users multiplex a frequency domain resource in this system. If HARQ information is transmitted by using the method in the LTE system, HARQ information of users may be overlapped, and therefore, a base station cannot perform decoding by using the decoding method in LTE. Therefore, for a system in which multiple users multiplex a frequency domain resource, the existing method for transmitting HARQ information on a PUSCH channel is no longer applicable.